1. Field of the Invention
The present invention relates to a non-contact electric power supplying system for supplying electric power to a vehicle on a non-contact basis.
2. Description of the Related Art
Electrically powered vehicles, such as electric train carriages and monorails, electric vehicles and vehicles that convey parts and so forth in factories, are known. As one of means for supplying electric power to such electrically powered vehicles, a charging station system has been implemented. In the charging station system, however, whenever electric power of the battery of the vehicle begins to run out, the user thereof should drive the vehicle to a charging station and charge it with electric power. Thus, when a parts conveying system in a factory is operated using such a charging system, the operation efficiency is low. Consequently, when an electrically powered vehicle travels only over a predetermined route, a more effective system is desired. To solve this problem, an electric power supplying system is used.
In the electric power supplying system, as in electric trains and monorails, a contact-type of electric power supplying system has been widely implemented. However, in this system, since the contact portions get worn, they should be maintained and periodically replaced with new ones. Moreover, in the contact-type electric power supplying system, since the contact portions are subject to sparking, such a system cannot be used in an explosion-protected area, such as an area with an oily atmosphere.
To solve such problems, non-contact type electric power supplying systems have been developed and implemented. Next, a prior art non-contact type electric power supplying system using a feeder will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a conveying system that supplies electric power from a feeder on a non-contact basis. In FIG. 1, a guide rail 4 is disposed on a route of a vehicle 3 (denoted by dashed lines). A feeder 5 is disposed along the guide rail 4. The feeder 5 is a conductor wire such as a copper wire coated with an insulation material. The feeder 5 is routed from a start point X of the guide rail 4 to an end point Y thereof. AC current is supplied from an AC power supply 1 to the feeder 5. The vehicle 3 has an electric power receiving unit 2 that receives electric power from the feeder 5 on a non-contact basis. With the electric power received by the electric power receiving unit 2, the vehicle 3 travels from the start point X to the end point Y of the guide rail 4.
FIG. 2 is a partial sectional view showing the conveying system shown in FIG. 1. FIG. 2 shows principal portions including the electric power receiving unit 2 and the feeder 5 for explaining an electric power supplying method according to a related art reference.
The guide rail 4 has a guide portion 6 that guides the vehicle 3. In addition, the electric power receiving unit 2 has guide rollers 7 that clamp the guide portion 6 of the guide rail 4 from both sides. When the vehicle 3 travels, the guide rollers 7 rotate. In other words, the vehicle 3 travels along the guide rail 4. Here, the distance between the vehicle 3 and the guide rail 4 is constant.
The guide rail 4 has an outbound portion and an inbound portion of the feeder 5. The feeder 5 is held by support members 10 secured to the guide rail 4. In other words, the feeder 5 is disposed at a distance from the guide rail 4 by the support member 10. As shown in FIG. 1, the feeder 5 supplies current from the AC power supply 1 so that the current is returned at the end point Y. In FIG. 2, the directions of the currents that flow in the outbound portion and the inbound portion of the feeder 5 are always opposite to each other.
The electric power receiving unit 2 has an E-shaped magnetic material core 8. The E-shaped magnetic material core 8 is made of, for example, silicon steel or ferrite and formed in the shape of the letter E. The E-shaped magnetic material core 8 has a secondary coil 9 on the center support portion thereof.
When the vehicle 3 is placed on the guide rail 4, the outbound portion and the inbound portion of the feeder 5 are disposed in respective groove portions of the E-shaped magnetic material core 8. In this state, when an AC current is supplied to the feeder 5, the AC current causes an alternating magnetic field to be generated. The alternating magnetic field penetrates the E-shaped magnetic material core 8. Thus, due to the electromagnetic induction, the alternating magnetic field causes the secondary coil 9 to generate electromotive force. Electric power generated in the secondary coil is supplied to the vehicle 3. When the vehicle 3 travels, the electric power causes the guide rollers 7 to be rotated in a predetermined direction. Alternatively, the electric power causes tires (not shown) of the vehicle 3 to be rotated. In such a manner, the electric power is supplied from the feeder 5 to the vehicle 3 on a non-contact basis.
To allow the electric power receiving unit 2 to effectively receive electric power from the feeder 5, it is important to optimize the relative position between the feeder 5 and the E-shaped magnetic material core 8. In other words, as shown in FIG. 3A, when the distance between the feeder 5 and the E-shaped magnetic material core 8 is a predetermined value, the electric power receiving unit 2 can effectively receive electric power from the feeder 5. Thus, when the feeder 5 is too close to or far from the E-shaped magnetic material core 8, the electric power receiving unit 2 cannot effectively receive electric power.
The guide rail 4 that guides the vehicle 3 is not always straight along all of a route. Normally, the route of the guide rail 4 includes a curved portion. In addition, the E-shaped magnetic material core 8 has a length dimension in the traveling direction of the vehicle 3 (namely, the direction along the guide rail 4 or the direction perpendicular to the plane of the drawing of FIG. 3A). Thus, when the vehicle 3 travels on a curved portion of the guide rail 4, as shown in FIG. 3B, and if the relative position between the feeder 5 and the E-shaped magnetic material core 8 is optimized at the center portion of the E-shaped magnetic material core 8 in the direction along the guide rail 4, the relative position between the feeder 5 and the E-shaped magnetic material core 8 becomes improper at the end portions of the E-shaped magnetic material core 8 in the direction along the guide rail 4. Thus, the leakage flux increases, and the electric power receiving unit 2 cannot satisfactorily receive electric power. Consequently, the traveling speed of the vehicle 3 decreases or the traveling operation thereof becomes unstable.